A dual indentation method for evaluating intrinsic material properties of metals under residual stress

Abstract

A dual flat-spherical indentation (DFSI) method is proposed for evaluating elastic-plastic properties of metallic materials under equi-biaxial residual stress (RS) state. DFSI consists of two indentation steps: (step I) performing flat indentation (FI) on a specimen having significant presence of residual stress, and (step II) performing spherical indentation (SI) at the center of residual imprint generated by the FI (step I). Indentation load-depth curve in conventional single spherical indentation (SSI) generally varies with RS, while the load-depth curves of SI step in DFSI are almost identical even under significant RS; this is attributed to stress redistribution during the preceding FI step. A set of FE analyses are performed for a wide range of properties of general metals. Regression-based mapping functions are established for evaluating the elastic-plastic properties from the SI data of step II. Finally, the proposed method is validated by performing DFSI experiments on the mechanically stressed SM45C and SS400 specimens.

Keywords

• Indentation
• Finite element analysis
• Residual stress
• Material property
• DFSI